The structural distortion of the anti-perovskite nitride Ca3AsN

(La3 Z x)Al and (Ce3 Z x)Al with Z = C, N, O: preparation, physical properties and chemical bonding of metal-rich perovskites

“…Distortion typically proceeds by static tilting of the octahedra at somewhat lower temperatures or higher pressures. For comparison, the closely related cubic Perovskite nitride (Ca 3 N)Tl exhibits nearly no anisotropy of Ca (U 11 ≈ U 33 [43]), indicating a perfect size fit, while, e. g., the nitrides (Ca 3 N)E with E = P, As [44,45] and the oxides (A 3 O)E with A = Ca, Sr, Ba and E = Si, Ge [46 -48] are distorted to orthorhombic unit cells (space group Pnma). The unit cell volumes of the carbides are significantly larger than those of the nitrides, oxides, and particularly the binary (hexagonal) phases.…”

Alkaline‐earth Metal Nitrides of the Main‐Group Elements: Crystal Structures and Properties of Inverse Perovskites

“…The internal angles and distances in (Ca 3 N)As even at 15 K indicate the octahedra to be truly rigid [d(Ca-N) = 240 pm with deviations below 1 pm and Ͻ(Ca-N-Ca) = 90°/180°with deviations below 0.2°]. [52] Similar distortions were observed for the corresponding oxides (A 3 O)E (A = Ca, Sr, Ba; E = Si, Ge). [24,27,28] Noteworthy, such Figure 2.…”

“…[17][18][19][20][21]23,[50][51][52] Temperatures applied range from 700°C to 1300°C depending on the element combination with dwelling times as short as 10 h to well above 2 d. A widespread of reaction vessels has been found appropriate, starting with open alumina and transition metal crucibles for reactions in nitrogen atmosphere and extending to sealed fused silica tubes and metal capsules. Sealed vessels can be used if sufficient or especially the exact desired amount of nitrogen for compound formation is already contained within the starting materials, for example via use of binary alkaline-earth metal nitrides.…”

“…[18] A similar distortion was observed for the Perovskites (Cs 3 O)Cl [36] and (K 3 O)Cl [35] with the latter suffering a phase transition to cubic at 364 K. While the distortion in (Ca 3 N)As increases with decreasing temperature or increasing pressure, there are indications that at elevated temperatures the distortion is reduced, respectively the compounds become cubic. [52,78] Figure 2 shows the rotation of rigid (Ca 6/2 N) 3+ octahedra (Glazer notation a -a -c + [45,46] ). The internal angles and distances in (Ca 3 N)As even at 15 K indicate the octahedra to be truly rigid [d(Ca-N) = 240 pm with deviations below 1 pm and Ͻ(Ca-N-Ca) = 90°/180°with deviations below 0.2°].…”

“…Top: Cubic undistorted view of the Perovskite structure; bottom: octahedra orientation in orthorhombic (Ca 3 N)As (at 305 K, view along the orthorhombic c axis). [52] Light gray spheres: Ca, medium gray spheres: As, dark gray spheres: N. Octahedra Ca 6 N are shown. distortions were only observed for the semiconducting compounds discussed in this paragraph, while for metallic (anti) Perovskite phases of the considered type exclusively cubic Perovskites were reported so far.…”